/-\    \    '■!  '     <    '    f 


Ismi.-.I  Mav  I,  190* 


U.S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  PLANT  INDUSTRY     Circular  tfo.  7. 

B.    r.  G  \U.>  'WAY,  chief  of  Bureau. 


THE   FIELD  TREATMENT  OF 
TOBACCO  HOOT-HOT. 


I.V.MAN  J.   BRIGGS, 
Physicist  in  Charge  of  Physicai    Laboratory. 


3U99G— OS 


WASHINGTON  :  GOVERNMENT  PRINTING  OFFICE  :  1908 


l 

r\+s*r\ 

US  DEPOSITORY 

BUREAU  OF  PLANT  INDUSTRY. 

Pathologist  and  Physiologist,  and  Chief  of  Bureau ,  Beverly  T.  Galloway. 
Pathologist  and  Physiologist,  and  Assistant  Chief  of  Bureau,  Albert  F.  Woods. 
Laboratory  of  Plant  Pathology,  Erwin  F.  Smith,  Pathologist  in  Charge. 
In  1 1  -i  ligations  of  Diseases  of  Fruits,  Merton  B.  Waitc,  Pathologist  in  Charge. 
Laboratory  of  Forest  Pathology,  Haven  Metealf,  Pathologist  in  Charge. 
Truck  Crop  Diseases  and  Plant  Disease  Survey,  William  A.  Orton,  Pathologist  in  Charge. 
Plan/  Life  History  Investigations,  Walter  T.  Swingle,  Physiologist  in  Charge. 

Cotton  Breeding  Investigations,  Archibald  D.  Shame]  and  Daniel  N.  Shoemaker,  Physiologists  in  Charge. 
Tobacco  Investigations,  Archibald  D.  Shame],  Wightman  \Y.  Garner,  and  Ernest  H.  Mathewson,  in 

Charge. 
Corn  Investigations,  Charles  P.  Hartley,  Physiologist  in  Charge. 
Alkali  and  Drought  Resistant  Plant  Breeding  Investigations,  Thomas  II.   Kearney,   Physiologist  in 

Charge. 
Soil  Bacteriology  and  Water  Purification  Investigations,  Karl  F.  Kellerman,  Physiologist  in  Charge. 
Bionomic  Investigations  of  Tropical  and  Subtropical  Plants,  Orator  F.  Cook,  Bionomist  in  Charge. 
Drug  and  Poisonous  Plant  Investigations  and  Tea  Culture  Investigations,  Rodney  H.  True,  Physiologist 

in  Charge. 
Physical  Laboratory,  Lyman  J.  Briggs,  Physicist  in  Charge. 

Crop  Technology  and  Fiber  Plant  Investigations,  Nathan  A.  Cobb,  Crop  Technologist  in  Charge. 
Taxonomic  and  Range  Investigations,  Frederick  V.  Coville,  Botanist  in  Charge. 
Farm  Management  Investigations,  William  J.  Spillman,  Agriculturist  in  Charge. 
Grain  Investigations,  Mark  Alfred  Carleton,  Cerealist  in  Charge. 
Arlington  Experimental  Farm,  Lee  C.  Corbett,  Horticulturist  in  Charge. 
Vegetable  Testing  Gardens,  William  W.  Tracy,  sr.,  Superintendent. 
Sugar-Beet  Investigations,  Charles  O.  Townsend,  Pathologist  in  Chargi 
Western  Agricultural  Extension  Investigations,  Carl  S.  Scofield,  Agriculturist  in  Charge. 
Dry-Land  Agriculture  Investigations,  E.  Charming  Chilcott,  Agriculturist  in  Charge. 
Pomological  Collections,  Gustavus  B.  Brackett,  Pomologist  in  Charge. 
Field  Investigations  in  Pomology,  William  A.  Taylor  and  G.  Harold  Powell,  Pomologists  in  Charge. 

•  •  menial  Gardens  and  Grounds,  Edward  M.  Byrnes.  Superintendent. 
Fori  ign  Seed  and  Plant  Introduction,  David  Fairchild,  Agricultural  Explorer  in  Charge. 
Forage  Crop  Investigations,  Charles  V.  Piper,  Agrostologist  in  Charge. 
Seed  Laboratory,  Edgar  Brown,  Botanist  in  Charge. 
Grain  Standardization,  John  D.  Shanahan,  Expert  in  Charge. 

Subtropical  Laboratory  and  Gardi  n,   Miami,  Fla.,  Ernst  A.  Bessey,  Pathologist  in  Charge. 
Plant  Introduction  Garden,  Chico    Cal.,  August  Mayer,  Expert  in  Charge. 
South  Tuns  Garden,  Brownsvilh     'fix..  Edward  C.  Green,  Pomologist  in  Charge 
Farmers'  Coopt  rative  Demonstration  Work.  Seaman  A.  Knapp,  Special  Agent  iu  Ch 
Seed  Distribution  (Directed  by  Chief  of  Bureau),  Lisle  Morrison,  Assistant  in  General  Charge. 


/./   or,  .1.  !■'..  Rockwell. 
Chit     Clerk,  James  E   Jones. 

[Circ.  7.  | 
2 


CON  T  i:  NTS 


Page. 

Nature  of  root-rol 5 

Field  treatment  of  root-rot....         5 

Occurrence  of  root-rol 6 

Field  experiments  showing  the  bad  effects  of  alkaline  commercial  fertilizers 

c.n  root-rol  soils 6 

i  rreenhouse  experiments  with  alkaline  fertilizers 7 

Summarj   

[Circ.7.]  3 


Digitized  by  the  Internet  Archive 
in  2013 


http://archive.org/details/fieldtrOOunit 


B.  P.  I.— 373. 


THE  FIELD  TREATMENT  OF  TOBACCO 

ROOT- ROT. 


NATURE  OF  ROOT-ROT. 

During  the  past  few  years  a  disease  known  as  root-rol  has  made 
its  appearance  in  the  tobacco  fields  in  some  districts  of  Kentucky, 
Connecticut,  Ohio,  and  Wisconsin.  This  disease  is  now  generally 
recognized  to  be  due  to  a  soil  fungus0  {Thielavia  basicola),  which 
attacks  the  feeding  roots  of  the  tobacco  as  fast  as  they  arc  thrown 
out.  The  root-rol  generally  makes  its  first  appearance  in  the  field 
in  spots,  particularly  low  spots,  and  may  later  develop  throughout 
the  field.  The  most  striking  feature  is  the  failure  of  the  plants  to 
make  a  proper  growth.  The  diseased  plants  are  often  only  8  or  10 
inches  high  when  healthy  plants  set  at  the  same  time  are  ready  to  he 
cut.  These  small  plants  will  he  found  to  have  onl\  a  small  hall  of 
stubby  roots,  and  the  fungus  can  he  seen  on  the  blackened  or  brownish 

ends   of  the   roots,    which   in    the   active   stages  of  the   disease    have   a 
rotted  appearance. 

Root-rol  has  already  been  successfully  checked  in  the  seed-bed  by 
Selby6  with  the  use  of  formalin,  and  by  Shamel''  through  sterilization 
by  steam.  Nether  of  these  methods  can  he  considered  practicable 
for  treating  the  disease  in  the  Held.  In  experiments  made  last  year 
l>\  \Y.  W.  Gilbert  and  the  writer,  a  formalin  solution  applied  to 
a  one-tenth  acre  plot  of  diseased  land  at  the  rati'  of  .".nil  pounds  of 
formalin  per  acre''  gave  somewhat  increased  yields,  hut  not  suffi- 
cient  to  justifj  the  expense  involved. 

FIELD  TREATMENT  OF  ROOT-ROT. 

The  objeel  of  this  circular  is  to  give  briefly  the  preliminary  results 
of  the  writer's  efforts  to  overcome  the  attacks  of  this  fungus  on  the 
tobacco  in  the  field  by  the  proper  use  of  fertilizers,  with  the  hope 

Sei     •  by   Selby,  of    the   Ohio    Agricultural    Experiment    Station,  and  by 

Clinton,  of  the  Connecticut  Agricultural  Experiment  Station.     Mr.  \V.  W.  Gilbert,  of 
the  Department  of  Agriculture,  I  as  a  bulletin  on  this  subjeel  in  preparation. 
^Circular  No.  59,  <>hi'>  Agricultural  Experiment  Station, 
c  Bulletin  No   91,  Bureau  of  Plant  Industr     Department  of  Agricultun     LSOl 
i  ins  would  represent  a  cost  of  about  $60  per  acre  for  the  formalin  alone. besides 
ibor. 
[Clrc7.] 


b  FIELD    TREATMENT    OF    TOBACCO    ROOT-ROT. 

that  the  suggestions  offered  can  be  utilized  this  season  by  tobacco 
growers  who  have  fields  affected  with  this  disease.  The  results  of 
the.  writer's  investigations  thus  far  indicate  that  the  tobacco  is 
much  more  severely  injured  by  the  fungus  on  fields  where  the  soil 
has  been  made  alkaline  by  the  long-continued  use  of  large  amounts 
of  lime,  ashes,  and  fertilizers  containing  carbonate  of  potash.  The 
remedy  for  diseased  soils  appears,  then,  to  consist  in  avoiding  the 
use  of  lime  and  in  applying  the  necessary  potash  in  the  form  of  the 
sulphate  of  potash,  which  is  a  neutral  salt  ;  and.  if  the  field  is  badly 
diseased,  in  applying  the  phosphoric  acid  in  the  form  of  acid  phos- 
phate in  order  to  help  neutralize  the  alkalinity  of  the  soil.  The 
above  view  as  to  the  cause  of  the  development  of  the  disease  in 
some  of  the  tobacco  fields  of  Connecticut  is  in  harmony  with  field 
observations,  as  will  appear  in  the  following  pages. 

OCCURRENCE  OF  ROOT-ROT. 

The  fungus  causing  this  disease  is  one  commonly  found  in  leaf 
mold  and  decaying  organic  matter,  and  therefore  may  reasonably 
be  expected  in  any  new  land.  The  fact  that  the  disease  does  not 
occur  on  tobacco  fields  until  they  have  been  in  tobacco  for  several 
years  indicates  that  the  fungus  may  be  present  in  the  soil  without 
attacking  the  tobacco.  If  we  grant  this  point,  then  some  condition 
which  favors  the  development  of  the  fungus  on  the  tobacco  roots 
must  develop  in  the  soil  after  several  crops  of  tobacco  have  been 
grown. 

Root-rot  in  the  Connecticut  Valley  is  especially  prevalent  in  fields 
on  which  unusually  large  quantities  of  fertilizers  have  been  used.  The 
development  of  the  disease  is  not.  however,  due  to  too  high  a  per- 
centage of  soluble  salts  in  the  soil.  This  point  was  tested  both  in  the 
greenhouse  and  in  the  field,  and  it  was  found  that  the  growth  of 
tobacco  upon  diseased  soils  was  1  tetter  when  a  liberal  quantity  of 
neutral  fertilizers  was  used  than  when  smaller  amounts  were  employed. 
If  the  root  system  of  the  tobacco  is  greatly  reduced  by  the  root-rot, 
the  plants  that  are  fertilized  liberally  and  thus  have  a  large  amount 
of  available  plant  food  immediately  at  hand  will  make  the  best 
growth.  Heavy  fertilizing  will  not  overcome  the  effects  of  the  root- 
rot,  however,  and  if  alkaline  fertilizers  are  used  the  growth  will  actu- 
ally be  decreased,  as  the  following  experiments  show: 

FIELD  EXPERIMENTS  SHOWING  THE  BAD  EFFECTS  OF  ALKALINE 
COMMERCIAL  FERTILIZERS  ON  ROOT-ROT   SOILS. 

During  the  season  of  1907  a  series  of  fertilizer  experiments  were 

tried  on  two  diseased   fields  in  the  Connecticut    \  alley.     These  tests 

were  confined  mainly  to  fertilizers  which  have  been  extensively  used 

in   tobacco  growing  in  Connecticut.      No   acid    ^alt^  or  ready-mixed 
[Circ.  7.J 


FIELD     I  IM   \  I  M  I  N  I     '"      rOBACCO    RO( '  I    i  7 

fertilizers  were  used.  While  none  of  the  fertilized  plots  on  the  badly 
diseased  fields  gave  yields  equal  to  those  obtained  from  adjacenl  lie  It  Is 
free  from  disease,  large  differences  in  yield  were  obtained  from  the 
fertilized  plots.  In  .-ill  cases  ii  was  found  thai  the  plots  on  which 
carbonate  of  potash  was  used  gave  the  smallest  plants  and  the  lowest 
yields.  The  use  of  lime  with  the  carbonate  of  potash  still  further 
diminished  the  yield.  The  use  of  carbonate  of  potash  and  lime  with 
cotton-seed  meal  and  ground  fish  gave  a  yield  of  bu<  900  pounds  per 
acre.  This  yield  was  200  pounds  less  to  the  acre  than  when  no  fer- 
tilizer was  used  and  was  only  a  little  more  than  half  the  yield  obtained 

from  soi f  the  other  plots.     These  results  indicate  thai  the  alkaline 

condition  of  the  soil  resulting  from  the  use  of  carbonate  of  potash  and 
lime  favored  the  development  of  the  root-rot. 

GREENHOUSE  EXPERIMENTS  WITH  ALKALINE  FERTILIZERS. 

The  ell'ert  of  alkaline  fertilizers  was  tested  further  in  a  series  of 
greenhouSe  experiments  made  with  a  diseased  soil  from  Connecti- 
cut. All  the  pots  were  fertilized  uniformly  with  cotton-seed  meal. 
To  some  of  the  pots  one-half  per  cent  of  air-slaked  lime  was  also 
added.  This  cut  down  the  weighl  of  tobacco  to  nearly  one-half 
(53  per  cent  |.  Adding  2  per  cent  of  lime  decreased  the  weight  to 
:;.")  per  cent  of  thai  of  the  check  plots.  In  soils  free  from  root-rot. 
the  use  of  1  per  cent  of  lime  gave  a  better  growth  of  tobacco  than 
when  no  lime  was  used.  This  shows  that  the  lime  does  not  injure 
the  tobacco  directly.  The  application  of  land  plaster  to  the  dis- 
eased -oil  iii  amounts  varying  from  one-half  of  1  per  cent  to  2  pel- 
cent  hail  no  had  effects  and  even  slightly  increased  the  growth  of 
tobacco.  When  lime  was  used  with  land  plaster  the  weighl  again 
decreased,  averaging  about  in  per  cent  of  that  of  the  checks.  The 
use  of  carbonate  of  potash  in  addition  to  the  cotton-seed  meal 
decreased  the  weight  of  the  tobacco  to  about  so  per  cent  of  the 
checks  in  spite  of  the  fact  that  additional  plant  food  was  added. 
The  use  of  hydrochloric  acid,  on  the  other  hand,  increased  the  yield 
1>\   about   in  percent,  although  this  acid  carries  no  plant  food. 

The  plants  in  the  check  pots  in  these  experiments  made  a  good 
growth  and  were  not  seriously  injured  by  the  root-rot.  although  the 
fungus  could  he  seen  on  the  roots.  The  root  systems  of  the  plants  in 
all  the  pots  to  which  lime  or  carbonate  of  potash  was  added  were 
badly  diseased.  The  roots  of  the  plants  grown  in  the  soil  in  ■ 
land  plaster  was  used  showed  some  disease,  about  like  that  of  the  check 
pots.  The  roots  of  the  plants  grown  in  the  acid-treated  soil  were  per- 
fectly clean  and  white,  and  entirely  free  from  the  fungus. 

The  soil  used  was  originally  from  a  badly  diseased  field.  For  a  year 
prior  to  these  experiments  it  was  used  for  grow  ing  tobacco  in  shallow 
greenhouse    beds    provided    with    ur<>"<!    drainage.     This   treatment 

[Ore.  7.  J 


8  FIELD    TREATMENT    OF    TOBACCO   ROOT-ROT. 

greatly  reduced  the  effect  of  the  root-rot,  The  improvement  was 
doubtless  due  in  part  to  the  leaching  away  of  the  lime  in  watering. 
The  sandy  tobacco  soils  of  Connecticut,  which  leach  readily,  are  not 
affected  with  root-rot.  It  is  highly  significant  that  the  root-rot  in  this 
soil  reestablished  itself  with  all  its  old  vigor  when  the  soil  was  made 
alkaline  through  the  addition  of  lime. 

SUMMARY. 

The  tobacco  root-rot  is  caused  by  a  soil  fungus. 

The  fungus  attacks  the  tobacco  roots  most  severely  when  the  soil 
has  become  alkaline,  due  to  the  use  of  too  large  amounts  of  lime, 
ashes,  or  fertilizers  containing  carbonate  of  potash. 

Remedy.— -Use  no  lime  on  diseased  fields.  Apply  potash  in  the  form 
of  sulphate  of  potash  or  double  manure  salts.  Apply  phosphoric 
acid  in  the  form  of  acid  phosphate  or  dissolved  bone  to  correct 
the  alkalinity  of  the  soil.     Plaster  can  be  used  if  desired. 

Where  other  land  is  available  for  tobacco,  use  the  diseased  fields  for 
some  other  crop  for  a  year  or  more.  Use  no  lime  or  alkaline  form  of 
fertilizer  until  the  roots  of  the  tobacco  are  free  from  the  disease. 
Lime  and  alkaline  fertilizers  can  then  be  used  cautiously. 

[Circ.  7.] 

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